I got Rodney to respond to this on Twitter:
https://twitter.com/wotc_rodney/with_replies
I really appreciate him answering me, but I disagree with just about everything.
1) True, it's a fixed and limited grouping, but the spell lists are incredibly powerful and gives you access to spells that sorcerers don't usually get. For example, Light domain gets Bless and Cure Wounds at 1st level, then Less Restoration and Spiritual Weapon at 3rd. These spells are better at what they do than any Sorcerer equivalent. Even if you pick Light Domain, which has a decent amount of overlap with sorcerer spells (burning hands, scorching ray), you're still picking up things like Faerie Fire, Flaming Sphere, again better than any Sorc equivalent. And also if you wanted spells like Burning Hands or Scorching Ray anyway, it frees up a choice for you from the Sorc list to take something else.
2) The FS's abilities definitely match up to the raw potency of the other Origins and just as "narrow." Half Plate + Shield is 17 AC -- you have higher AC than a Dragon Sorcerer's even if both had max DEX (FS 19, Dragon 18). Wings vs. Wings. Extra Attack (essentially double damage for your melee) vs. +CHA on specific blasting spells (varaible % increase, very good though) vs. the underwhelming "Bend Luck."
3) He doesn't realize that +66% spells known increase is severely downplaying it (that's at max level). At levels 1, 3, 5, 7, 9, it's a +100% increase in spells known. That's insane.
We'll see if he responds or not.